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Set up a machine and its arms

Describes RotoSpider Desktop 0.8.13 · checked 2026-09-13 D5

To RotoSpider, a machine is one or two arms with a handful of numbers from the machine maker's drawing or a tape measure. This page shows where they go; the next two pages, a straight arm and an offset or L arm, explain each number, how to measure it, and what the layout does with it.

The two kinds of arm

Every arm turns two ways at once: the arm tube turns about its own axis, and the plates turn about the axis through their centres, driven by a shaft inside the hollow tube through a right-angle gear at its end.

A straight arm is a tube that comes into the oven along its axis of rotation and ends in a hub carrying two spiders, one on each side of the hub. Molds mount on the outer face of each spider, and the whole set must stay inside a ball, the rotation envelope, centred on the arm's axis.

An offset or L arm is the same tube cranked: it bends down outside the mold space and carries one spider from underneath, so molds mount on the one outer face of the single plate, one uninterrupted mounting space instead of two, each half the height. The ball they must stay inside is centred on the arm's axis, above the plate, and its sides are cut off at the width the crank leaves free. Chinese factories call it the L 臂 or 偏心臂.

The app tells them apart by which columns of the workbook row are filled. A row with the straight columns is a straight arm; a row with the offset columns is an offset or L arm; a row with both becomes two arms in the app, one of each, under the same model name.

The Spider / Arm Data tab

The grid has one row per arm. With the trial workbook it shows the five sample machines, all straight:

With a workbook whose rows carry both variants, the same model appears twice, once as Straight and once as Offset/L:

The columns, left to right, and the workbook column each one comes from:

The Chinese workbook headers are also read: 直臂加热室回转空间直径/mm, 直臂模盘直径/mm, 直臂无效空间高/mm, L臂回转空间纵向直径/mm, L臂模盘直径/mm, L臂模盘Y/mm, L臂回转空间横向直径/mm, L臂增高架高/mm.

Edit Max load (kg) directly in the grid, then press Save to write it to the workbook. Clear the cell or enter 0 to remove the load limit. The value remains when you reopen the app. An offset or L arm's spider Y offset, in Dead height / spider Y (mm), must be greater than zero; the grid refuses zero and keeps the saved value.

The preview

The panel on the right draws the selected arm from its numbers: the plate, the envelope ball, the dead height or the riser, with the values under it. Click a row to select it, drag the drawing to turn it. When a number is wrong the drawing usually shows it before a layout does: a plate wider than its ball, a ball that barely clears the plate.

Adding a machine

Add a row to the machines sheet in Excel with the model name and the measurements of its arm, save, and press Reload on the layout tab. The new model appears in the Machines list and in this grid. The tab itself edits the numbers of existing rows; it does not add rows.

What the layout does with these numbers

Each parameter is a rule the layout keeps: molds stay inside the ball, inside the plate's circle, out of the dead height, under the load cap. When a mold breaks one, it goes to the staging area and the status strip says which rule it broke. The two pages that follow give, for every parameter, the rule and what a wrong number does.